Fluid-fluid phase separation in hard spheres with a bimodal size distribution

TL;DR

This paper investigates how polydispersity affects phase separation in hard spheres with bimodal size distributions, revealing conditions for spinodal instability and dense large-sphere phases.

Contribution

It introduces a moment projection method to analyze phase behavior, identifying specific conditions for instability in bimodal distributions.

Findings

Spinodal instability occurs with sufficient polydispersity and size disparity.

A very dense phase of large spheres emerges at instability.

The Boublik-Mansoori-Carnahan-Starling-Leland equation predicts these phenomena.

Abstract

The effect of polydispersity on the phase behaviour of hard spheres is examined using a moment projection method. It is found that the Boublik-Mansoori-Carnahan-Starling-Leland equation of state shows a spinodal instability for a bimodal distribution if the large spheres are sufficiently polydisperse, and if there is sufficient disparity in mean size between the small and large spheres. The spinodal instability direction points to the appearance of a very dense phase of large spheres.